The present invention relates to a liquid-propellant weapon of the type having a system for injecting a liquid propellant agent into a combustion chamber delimited between a projectile loaded into the barrel of the weapon and a breechblock that closes off the rear end of the barrel. The injection system includes at least one reservoir communicating with the chamber and containing the propellant agent, a piston movable inside the reservoir, and a device that initiates combustion of a small quantity of propellant agent injected directly into the chamber. The injection system uses the pressure of the combustion gases in the chamber to cause displacement of the piston and bring about injection of the propellant agent stored in the reservoir into the chamber.
By comparison with a powder weapon, a liquid-propellant weapon has in particular the advantage of allowing continuous adjustment of the length of the projectile trajectory as a function of the volume of propellant agent injected into the chamber, which volume can be precisely defined. In addition, a liquid-propellant weapon allows for better distribution of the pressure exerted on the projectile during its ballistic phase inside the barrel.